How Can I Build Cheapest Mining Rig?

I didn’t start mining but I would. I don’t have too much budget for this. I need the cheapest mining setup for? My last question; I found The G1 Ipollo mini only on eBay and it is quite expensive. some people recommended the company website, it said Sold Out! How can I start? How can I get the G1 Ipollo mini ?
Or do you have any idea for how can I build Mining Rig?